In many high technology manufacturing operations, such as those involving the production of metal oxide silicon (MOS) transistor circuits, it is essential that plant personnel carefully observe rules requiring them to rid themselves of all static electric charges. In a typical manufacturing plant, employees may be required to test their ESD overshoes and log the results of the test every time they enter and leave their work area. Unfortunately, this task takes time, employees are sometimes lax in complying and some consider the task onerous and intrusive.
A number of prior art patents have addressed the problem of discharging static electricity accumulation. For example, U.S. Pat. No. 5,632,255 discloses a testing wristlet seat which uses an oscillator circuit to test a test lead which is grounded to discharge the static electricity produced in a manufacturing procedure. The oscillator generates a frequency to sound an alarm when the user breaks the ground connection. In U.S. Pat. No. 5,519,384 the worker wears a conductive wrist strap, circuitry monitors the electric field at the operator's wrist, sounds a warning and records when a problems occurs. In U.S. Pat. No. 5,247,420 a voltage-controlled oscillator senses the voltage on a discharge capacitor, generates high voltage pulses the effect the removal of charge by means of air ionization. In U.S. Pat. No. 4,859,992 the integrity of ground connections to conductive workbench, floor mats and wrist straps are monitored and alarms are generated when the resistance to ground approaches a set value. In U.S. Pat. No. 4,800,374 conductive wrist bands, touch pads and shoe plates are monitored for resistance and indicator lights provide a display of whether a safe or hazardous condition exists. U.S. Pat. No. 4,745,519 discloses details of a stretchable wrist strap having two or more sections of conductive material and circuitry for monitoring whether any of the sections of conductive material are in contact with the wearer or if the connection to ground is broken.
While all of the foregoing devices operate satisfactorily, they are not quite adequate to assure, in a commercial environment, the ideal standard of conduct to which Paracelsus may have had in mind when he uttered the timeless words. "That we devote ourselves to God, is seen In living just as through no God there were". Simply stated, the prior art devices operate anonymously and therefore do not accommodate the requirements of management for assurance that each individual worker remain in compliance with ESD standards. In short, an identifiable audit trail of ESD compliance is required.